A method of brake control of a vehicle combination (2) composed of a tractor vehicle (4) with an electronically controlled braking system (5) and a trailer vehicle (6, 8) with a pneumatically controlled pneumatic braking system (7, 9), involves introducing the brake control pressure (p.sub.BC) of the trailer vehicle (6, 8) into a tractor brake control line (19) extending to a tractor vehicle-side brake coupling head (26) via an electronically controlled trailer control valve (13) of the tractor vehicle (4). At the beginning of a braking operation, a pressure pulse (34) exceeding a target brake control pressure (p.sub.BC_soll) is introduced into the tractor brake control line (19). The volume of a trailer brake control line (28, 29, 32) coupled to the brake coupling head (26) is ascertained, and the absolute value (p.sub.PI) and/or the duration (t.sub.PI) of the pressure pulse (34) introduced are/is established depending on the ascertained volume.

A method of controlling brake pressures in a trailer vehicle braking system which has a trailer brake module for controlling a braking force on a wheel or wheels on the trailer. The trailer brake module receives data inputs from sensors on the trailer and a control pressure from a towing vehicle in a control line. The braking system has a second ECU configured to receive sensor inputs from sensors on the trailer to communicate with the trailer brake module and with the towing vehicle. If the second ECU determines that the control pressure should be increased or decreased, the second ECU sends a request to the towing vehicle to increase or decrease the control pressure, respectively.

A trailer braking system includes a supply line, a spring brake that moves from an apply position to a release position, a spring brake control valve which controls the flow of fluid to the spring brake, an immobiliser having a brake release and immobilise positions which control the flow of fluid to the spring brake control valve, an auxiliary control valve having a system enabled configuration where the immobiliser is operable to move both to the brake release position in which the immobiliser permits fluid to the spring brake control valve and the spring brake control valve is operable to cause the flow of pressurised fluid into the spring brake, and an immobilise position where fluid is not permitted to the spring brake control valve, and in the system disabled configuration, the immobiliser is placed in the immobilise position.

Systems and methods allow for controlling brakes of a trailer coupled to a tractor. The systems and methods utilize an inversion valve input between an emergency brake controller and a trailer connection at the tractor. The inversion valve receives a supply air from an output of the emergency brake controller, and a control air output from a treadle valve of the tractor. Depending on the control air, the emergency brakes at the tractor may be released/activated to simulate service brake control without requiring connecting the tractor to the trailer service brake line.